Unix Commands

Question 1

ls

Answer 1

list directory contents

Question 2

cd

Answer 2

change directory

Question 3

mkdir

Answer 3

make directory

Question 4

cp [file1] [file2]

Answer 4

copys a file

Question 5

mv [file1] [file2]

Answer 5

move or rename a file

Question 6

/

Answer 6

root directory

Question 7

/usr

Answer 7

usr directory

Question 8

chmod 755 file

Answer 8

Changes the permissions of file to be rwx for the owner, and rx for the group and the world. (7 = rwx = 111 binary. 5 = r-x = 101 binary)

Question 9

ls -a

Answer 9

List all files in current directory including hidden files

Question 10

ls -l

Answer 10

list a directory in long ( detailed ) format

Question 11

cat filename

Answer 11

Dump a file to the screen in ascii.

Question 12

echo $SHELL

Answer 12

Denotes what shell you are using.

Question 13

export PROJECTS=/usr/local/projects

Answer 13

Defines the environment variable PROJECTS with the value /usr/local/projects.

Question 14

cd $PROJECTS

Answer 14

Changes your present working directory to the value of the environment variable PROJECTS

Question 15

echo $PROJECTS

Answer 15

Prints out the value of PROJECTS, or /usr/local/projects

Question 16

find . -name aaa.txt

Answer 16

Finds all the files named aaa.txt in the Current directory or any subdirectory tree.

Question 17

find / -name vimrc

Answer 17

Find all the files named ‘vimrc’ anywhere on the system.

Question 18

find search_path -name filename

Answer 18

Find command

Question 19

chown bruce file

Answer 19

Makes user bruce owner of file

Question 20

chown -R bruce dir

Answer 20

Makes user bruce owner of directory and everything in its directory tree.

Question 21

chgrp user file

Answer 21

Makes file belong to the group user.

Question 22

~

Answer 22

Home directory

Question 23

rm file1 [file2 …]

Answer 23

Remove or delete a file

Question 24

rm -r dir1 [dir2…]

Answer 24

recursivly remove a directory and its contents

Question 25

rmdir dir1 [dir2...]

Answer 25

remove an empty directory

Question 26

more filename

Answer 26

Progressively dump a file to the screen: ENTER = one line down, SPACEBAR = page down, q=quit

Question 27

head filename

Answer 27

Show the first few lines of a file.

Question 28

head -n filename

Answer 28

Show the first n lines of a file

Question 29

tail filename

Answer 29

Show the last few lines of a file.

Question 30

tail -n filename

Answer 30

Show the last n lines of a file. Show the last n lines of a file. Show the last n lines of a file.

Question 31

ls -ld *

Answer 31

List all the file and directory names in the current directory using long format. Without the "d" option, ls would list the contents of any sub-directory of the current. With the "d" option, ls just lists them like regular files.

Question 32

touch

Answer 32

Changes the date/time stamp of the file filename to the current time. Creates an empty file if the file does not exist. You can change the stamp to any date using

Question 33

users

Answer 33

List users currently logged in

Question 34

killall

Answer 34

Kill processes by name

Question 35

ps

Answer 35

process status

Question 36

tar

Answer 36

tape archive

Question 37

tar xv

Answer 37

Extracts (x) files from the default tape drive while listing (v = verbose) the file names to the screen.

Question 38

ping

Answer 38

Test a network connection

Question 39

who

Answer 39

Print all usernames currently logged in

Question 40

whoami

Answer 40

Print the current user id and name (`id -un')

Question 41

wget

Answer 41

Retrieve web pages or files via HTTP, HTTPS or FTP